Summary

Six vulnerabilities involving Access Control List (ACL) has been
discovered in multiple releases of Cisco IOS® Software Release for Cisco 12000
Series Internet Routers. Not all vulnerabilities are present in all IOS
releases and only line cards based on the Engine 2 are affected by them.

Affected Products

This section provides details on affected products.

Vulnerable Products

Only Cisco 12000 Series Internet Routers with line cards based on
Engine 2 are affected with these vulnerabilities. Not all line cards of a Cisco
12000 Series are affected by all vulnerabilities. Vulnerabilities are present
in the underlying technology an individual line card is based upon. That
technology is called "Engine". Currently Cisco is shipping line cards based on
the following Engines: 0, 1, 2, 3 and 4.

To determine what Engine your card is based on, you need to log on the
Cisco 12000 router and issue "sh diag" command while
in enable mode. The engine type will be displayed as "L3 Engine:
x" where x will be the corresponding number.

The following example shows the output for an Engine 2 based line card.

Products Confirmed Not Vulnerable

No other Cisco products are currently known to be affected by these
vulnerabilities.

Details

Six vulnerabilities were found in IOS releases that are supporting
Cisco 12000 platforms. Only line cards based on Engine 2 are affected.

CSCdm44976
ACL will not block non initial fragments of a packet. This Cisco bug
ID is adding a support for "fragment" keyword in the ACL. The
White Paper Access
Control Lists and IP Fragments describes how keyword fragment modifies
behavior of ACL.

CSCdu57417
The keyword "fragment" in the compiled ACL (Turbo
ACL) is ignored if a packet is destined to the router itself.

CSCdu03323
The implicit "deny ip any any" rule at the end of an
ACL is ignored if an ACL of exactly 448 entries is applied on an interface as
an outgoing ACL. An ACL with any other number of rules, greater or less than
448, is unaffected by this vulnerability.

CSCdu35175
A support for "fragment" keyword in an outgoing ACL
is added. Previously, only incoming ACL supported this keyword and outgoing ACL
was ignoring it.

CSCdt96370
An outbound Access Control List (ACL) may not block all intended
traffic on a router when an input ACL is configured on some, but not all,
interfaces of a multi port Engine 2 line card. The prerequisite is that, the
traffic in question, was not filtered by an inbound ACL on the ingress port. An
ACL applied at the ingress point will work as expected and block desired
traffic.

CSCdt69741
Packet fragments are not filtered by the ACL despite using
"fragment" keyword. The White Paper
Access Control
Lists and IP Fragments describes how keyword fragment modifies behavior
of ACL.

Workarounds

CSCddm44976

There is no direct workaround for this vulnerability. If feasible,
packet fragments may be filtered before they reach the GSR.

CSCdu57417

There is no direct workaround for this vulnerability. If feasible,
packet fragments may be filtered before they reach the GSR.

CSCdu03323

The workaround is to either shorten the ACL to be less than 448 lines
in length or to explicitly add rule "deny ip any
any" as the last statement.

CSCdu35175

The workaround is to transform an ACL to an incoming ACL instead of the
outgoing one.

CSCdt96370

Apply an ACL on all ports on the ingress line card. If a particular
port is supposed to not block any traffic, then apply the ACL of the form
access-list xy permit ip any any.

CSCdt69741

There is no direct workaround for this vulnerability. It is possible to
block the fragments on an intermediate router, if such exists, that should be
placed between the affected Cisco 12000 and the final target. The intermediate
router must not be another Cisco 12000 affected by the same vulnerability.

Fixed Software

Each row of the table describes a release train and the platforms or
products for which it is intended. If a given release train is vulnerable, then
the earliest possible releases that contain the fix and the anticipated date of
availability for each are listed in the "Rebuild", "Interim", and "Maintenance"
columns. A device running any release in the given train that is earlier than
the release in a specific column (less than the earliest fixed release) is
known to be vulnerable, and it should be upgraded at least to the indicated
release or a later version (greater than the earliest fixed release label).

When selecting a release, keep in mind the following definitions:

Maintenance

Most heavily tested and highly recommended release of any label in a
given row of the table.

Rebuild

Constructed from the previous maintenance or major release in the same
train, it contains the fix for a specific defect. Although it receives less
testing, it contains only the minimal changes necessary to effect the repair.

Interim

Built at regular intervals between maintenance releases and receives
less testing. Interim releases should be selected only if there is no other
suitable release that addresses the vulnerability, and interim images should be
upgraded to the next available maintenance release as soon as possible. Interim
releases are not available via manufacturing, and usually they are not
available for customer download from CCO without prior arrangement with the
Cisco TAC.

In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current hardware and
software configurations will continue to be supported properly by the new
release. If the information is not clear, contact the Cisco TAC for assistance
as shown in the following section.

Early deployment (ED) release for the Cisco 7200, 7500/7000RSP
and 12000 series routers for Service Providers (ISPs).

12.0(18.6)ST1

12.0(19.3)ST

12.0(19)ST

Vulnerability CSCdu03323

Rebuild

Interim**

Maintenance

12.0S

Core/ISP support: GSR, RSP, c7200

12.0(16)S2

12.0(17.5)S

12.0(17)S

12.0ST

Early deployment (ED) release for the Cisco 7200, 7500/7000RSP
and 12000 series routers for Service Providers (ISPs).

12.0(16.6)ST1

12.0(17.5)ST

12.0(17)ST

Vulnerability CSCdu35175

Rebuild

Interim**

Maintenance

12.0S

Core/ISP support: GSR, RSP, c7200

12.0(19.6)S

12.0ST

Early deployment (ED) release for the Cisco 7200, 7500/7000RSP
and 12000 series routers for Service Providers (ISPs).

12.0(19.6)ST

Vulnerability CSCdt96370

Rebuild

Interim**

Maintenance

12.0S

Core/ISP support: GSR, RSP, c7200

12.0(16)S1

12.0(17.1)S

12.0(17)S

12.0ST

Cisco IOS software Release 12.OST is an early deployment (ED)
release for the Cisco 7200, 7500/7000RSP and 12000 (GSR) series routers for
Service Providers (ISPs).

12.0(15.6)ST3

12.0(17.1)ST

12.0(16)ST

Vulnerability CSCdt69741

Rebuild

Interim**

Maintenance

12.0S

Core/ISP support: GSR, RSP, c7200

12.0(16.6)S2

12.0(17.3)S

12.0(17)S

12.0ST

Cisco IOS software Release 12.OST is an early deployment (ED)
release for the Cisco 7200, 7500/7000RSP and 12000 (GSR) series routers for
Service Providers (ISPs).

12.0(17.3)ST

12.0(18)ST

Notes

* All dates are estimates and subject to change.

** Interim releases are subjected to less rigorous testing than
regular maintenance releases, and may have serious bugs.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerabilities described in this advisory.

Cisco Security Vulnerability Policy

To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.

Revision History

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Cisco Security Vulnerability Policy

To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.